Inserter systems are typically used by organizations such as banks, insurance companies and utility companies for producing a large volume of specific mailings where the contents of each mail item are directed to a particular addressee. In many respects, a typical inserter system resembles a manufacturing assembly line. Sheets and other raw materials (e.g., enclosures and envelopes) enter the inserter system as inputs. Then, a plurality of different modules or workstations in the inserter system work cooperatively to process sheets until a finished mail piece is produced. Typically, inserter systems prepare mail pieces by gathering collations of documents on a conveyer. The collations are then transported on the conveyer to an insertion station where they are automatically stuffed into envelopes. After being stuffed with the collations, the envelopes are removed from the insertion station for further processing, such as automated closing and sealing of the envelopes, weighing of the envelopes, applying postage to the envelopes, and finally sorting and stacking the envelopes.
At the input end of a typical inserter system, rolls or stacks of continuous printed documents, called a web, are fed into the inserter system by a web feeder. As will be appreciated, the continuous web must be separated into individual document pages. This separation is typically carried out by a web cutter that uses a blade forming a part of guillotine cutting module to cut the continuous web into individual document pages. In one type of web cutter, the web is provided with sprocket holes on both sides thereof and is fed from a fanfold stack or a roll into the web cutter. The web cutter has a tractor with pins or a pair of moving belts with sprockets to move the web toward the guillotine cutting module for cutting the web cross-wise into separate sheets. Perforations are provided on each side of the web so that the sprocket hole sections of the web can be removed from the sheets prior to moving the cut sheets to other components of the inserter system. In an alternative type of web cutter, the continuous web is moved by a pair of control nips. Such a system is referred to as a pinless cutter because the web drive arrangement does not utilize drive tractors or belts having pins to advance a web having sprocket holes, as described above.
In the feed cycle of a web cutter, the web is advanced past the blade of the guillotine cutting module by a distance equal to the desired length of the cut sheet and is stopped. In the cut cycle of a web cutter, the blade lowers to shear off the sheet of paper, and then withdraws from the web. As soon as the blade withdraws from the web path, the next feed cycle begins. The feed and cut cycles are carried out in such an alternate fashion over the entire operation.
FIG. 1 is a schematic diagram of a portion of a prior art web cutter 5 that includes a cutter portion 10 and a web handler portion 15. As seen in FIG. 1, the cutter portion 10 includes a blade 20 for cutting the web 25 in the manner just described and a motor driven tractor set 30 for feeding the web 25 (received from a paper source (not shown)) to the blade 20 in cooperation with the web handler portion 15, described below. Throughput performance of existing web cutters such as the web cutter 10 is typically limited by the forces experienced by the web 25 just upstream of the blade 20, as well as forces experienced by the web 25 at the point of entry of the web 25 into the web cutter 5 from the paper source. For a given level of cut frequency, the period between consecutive cuts is a constant length of time and is generally comprised of an advance or feed web time added serially to a cut web time. Although some overlap between these two times is permissible, for more reliable paper control, the web 25 may be kept at rest from the time when the blade 20 actually starts cutting the web 25 to the time that the blade 20 has fully retracted to clear the web 25.
In order to accommodate the steady state stopping and starting of the web 25 at the cutter portion 10, which is paired with an upstream module that is typically delivering the web 25 from the paper source at a constant velocity, the web handler portion 15 is provided, which serves as a control loop. In particular, the web handler portion 15 includes a low mass dancer roller 35, which is loaded against the web 25 by a light spring (not shown) for keeping the web 25 taut. In addition, the web handler portion 15 may also include an upstream urge device 40 to help to pull the web 25 from the paper source. It is at the location of the dancer roller 35 where the web 25 typically breaks due to the snap action of the web 25 on the dancer roller 35. This snap action of the web 25 is created by the dancer roller 35 translating downward as the web 25 at the cutter portion 10 accelerates upward. The breakage of the web 25 at this point can be attributed largely to the mass of the dancer roller 35. However, a limitation of the dancer roller 35 is that its finite mass cannot be practically lowered further because it is required to span the entire web 25, while preserving structural integrity.
FIG. 2 is a schematic diagram of an alternative web cutter 50. The web cutter 50 includes a blade 55 for cutting a web 70, and a motor-driven primary web drive 60 that works cooperatively with a motor-driven web handling mechanism 65 for feeding the web 70 (received from a paper source (not shown)) to the blade 55. In addition, the web cutter 50 includes a vacuum box 75 for keeping the web 70 taut. During steady state operation, the primary web drive 60 executes a rapid start and stop motion profile with accelerations typically exceeding 40 G's for 36,000 cuts per hour operation with a 12-inch cut sheet length output. The period for such operation is 100 ms. Also during steady state operation, the web handling mechanism 65 operates at a constant velocity, but during stoppages (e.g., cutting operations), the web handling mechanism 65 is designed to execute with low accelerations. The web handling mechanism 65 may be used in conjunction with a high capacity vacuum box 75 capable of containing roughly 1 meter of the web 70. In that arrangement, the web 70 may undergo accelerations upstream of the vacuum box 75 that generally do not exceed 0.5 G's.
Notwithstanding the improved performance provided by the web cutter 50, breakages of the web 70 may sometimes occur near the entrance of the web cutter 50 even when the drive elements of the web handling mechanism 65 operate at constant velocity. That condition may be aggravated when a cart (not shown) is utilized to hold a fan-folded stacked paper source (i.e., as compared to a fan-folded stack resting on the floor or a roll unwinder, which may also be used). In particular, translating the web 70 up and over rollers and/or turn bars to clear the cart to deliver the web 70 to the entrance of the cutter 50 may result in high nominal forces on the web 70 and more susceptibility to breaks in the web 70 due to force disturbances, which can either be external to the system (e.g., air resistance) or internal to the system (e.g., stoppages of the web cutter 50). These force disturbances are superimposed on the already high nominal tensions of the web 70.
In addition, it has been observed that when a cart is employed for the paper source, every other fan-folded panel of the web 70 resulted in high peak instantaneous motor torques associated with the web handling mechanism 65 in order to maintain the web 70 at constant velocity. It is speculated that the high forces introduced for every other panel are due to a low pressure zone generated between a stationary wall that is located in the center of the conventional carts and a panel that is being rapidly pulled away from such a wall. This effect is illustrated in FIG. 3, which is a plot of relative torque commanded to an amplifier that drives the motor that is coupled to the web handling mechanism 65 (Y-axis) versus time in seconds (X-axis). As seen in FIG. 3, each torque peak is spaced by two panel lengths. Neglecting the effect of motor rotor and drive mechanism inertia, the plot shown in FIG. 3 provides an accurate representation of the instantaneous tensile forces on the web 70 observed in one arrangement.